Yarn preparation



I Patented Sept. 15, 1942 YARN PREPARATION John Blanchard Miles, In, Greenville, Del, aa-

signor tell. I. du Pont de Nemom's & Company, 1 Wilmington, DeL, a corporation of Delaware No Drawing. Application July 30, 1941,-

Serial No. 404,621

. I 9Claims. (eta-140) a This invention relates to yarn preparation, and more particularly, it relates to a process for setting the twist in a yarn comprising filaments of a synthetic linear polymer of the type disclosed in Carothers U. S. Patent No. 2,071,250.

. This invention will be described with particular reference to Nylon yarns, i. e., yarns comprising filaments of synthetic linear polyamides as disclosed in Carothers U. S. Patent No.

2,130,948'and U. S. Patent N0.'2,071,253. Since, 10

however, many of the other synthetic linear polymers disclosed in the above-mentioned Patent No. 2,071,250 are subject to the peculiar setting characteristics 01 Nylon and since they may with the present invention, the term- Nylon" Y is intended to include them as equivalents in the present invention.

The tendency of a twisted yarn to untwist is known as twist livelinessVand renders a yarn '20 diificult, if not impossible, tohandle in subsequent textile operations. It is known that the tendency of a twisted yarn to untwist on handling may be reduced by subjecting the yarn to treatment under hot, wet conditions. It is also known that Nylon yarn, as well as yarn comprising other synthetic linear polymers disclosed in Patent No. 2,071,250, is responsive to twistsetting treatment under hot, wet conditions.

For instance, it is disclosed in two Carothers 0 patents, U. S. Patents Nos. 2,130,948 and 2,157,116, that the twist in a Nylon yarn may be set by treatment with steam.

subsequent utility of the Nylon yarn. This is because. as isshownin Miles U. S. Patent No. 2,157,117, the treatment of a Nylon yarn with steam tends to impart a yarn-setting in the yarn 40 as well as a twist-setting. A yarn that has been yarn set will tend to retain the physical con-- figuration that it hadatthe"time ofyarmset;

ting. That is, a yarn which was straight when steam-treated will tend to remain straight, a 4

yarn which was looped will tend to remain in loops, etc. Sincev the yarn, aftertwist-setting, is usually knitted or woven into a fabric, the use of a yarn which has become yam-set during the twist-setting will result in the production of a fabric having poor stitch or weave formation because of this wiry tendency of the yarn to resume the configuration it had at the time of yam-setting. This phenomenon of yarn-setting does not take place inother natural and syn thetic yarns but seems to be specific to the abovementioned synthetic liner polymer yarns, particularly Nylon yarns. 4

It is known that subjecting a twisted Nylonyam to hot, wet conditions which are notas drastic as'the steam treatment will set the twist to a certain extent without yarn-setting. Such a process is disclosed in Miles 'U. S. Patent No. 2,157,119 in which it isshown that the twisted yarn may 'be' twist-set by exposing, it, while wound onpirns, to air at l F. and 78% relative humidity for one hour. In Sommaripa U. S. application, Serial No. 226,683, now U. S. Patent No. 2,251,962, there disclosed amethod of realso be advantageously processed in accordance '15 ducingthe livelinessof a twisted sewing thread 'by allowing the thread, after twisting, to stand under the same conditions as in U. S. Patent No.

2,157,119. According to the standard practice in twist-setting, the yarn in both these examples was treated while wound on a rigid support. However, the liveliness .of the twist was not sufficiently reduced by this process for easy subse-v quent handling. This is shown in the Somtwist so treated was too lively and that a fur-' ther treatment with boiling water was necessary. Such treatment, of course, had the disadvantage of yam-setting.

. Thus, it will be seen that a usefultwist-setting of" Nylon yarns has, heretofore, presented a difficult problem. On the one hand, if the yarn is subjected to a steam treatment, although the twist is set, yam-setting also'occurs. If, however, on the other hand, the package of yarn is subjected to somewhat milder conditions in order to avoid yam-setting, the twist is not set sufficiently and the yarn exhibits an unsatisfactory amount of twist liveliness. These diflic'ulties are particularly increased when the twisted yam isof fine denier and highly twisted, and it is these Nylon yams that have proved so advantageous i n rnany textile uses especially in the "production-ofshear, fullfashioned hosiery and crepe fabrics.

It is, therefore, an object of this invention to i provide a satisfactory process for setting a twist in Nylon yarn to substantially reduce twist livelines without imparting to the yarn objectionable yam-setting.

It is a further object of this invention to provide a. twisted Nylon yarn in whichthe twist liveliness has been reduced to a satisfactory degree without objectionably yam-setting the same.

Other objects of this invention will appear hereinafter.

These objects are accomplished, in general, by the twist-setting of the yarn under mild, hot, wet conditions while permitting the yarn to shrink, It has now been found that a Nylon yarn may be twist-set to very materially reduce its twist liveliness by subjecting the same to hot, wet conditions which are sufllciently mild to prevent objectionable yarn-setting if the yarn, during this processing, is maintained under a sufficiently relaxed condition to permit the same to. shrink. Neither the twist liveliness nor the yarn-set in a yarn produced in this manner will objectionably interfere with its use in textile operations.

It is not known whether the twist liveliness is reduced because of the effect of the hot, wet conditions or whether it is reduced because of the shrinkage that takes place in the yarn during this process. That the shrinkage is an important factor in reducing the twist liveliness of the yarn is shown by the fact that if'the yarn is shrunk by any means before twisting, it is very diilicult to set the twist later. Also, the residual shrinkage, that is, the shrinkage of which a yarn is capable after twist-setting, is proportional to the tension under which the yarn is kept while the twist-setting operation is being performed. Additionally, in any particular yarn, its residual shrinkage after twist-setting is directly proportional to its twist liveliness. That is, the lower the residual shrinkage of a twisted yarn, twisted from identicalfilaments, the lower the twist liveliness and thus the better twist-set the yarn.

In order that the process of this invention may be more clearly understandable the following examples are set forth, although it will be clearly understood that the invention is not limited to these specific embodiments. 7

Example I Thirty-denier, lo-filament, unsized polyhexamethylene adipamide yarn which has been twisted to 30 turns per inch was wound into skeins and twist-set at 170 F. and 88% relative humidity for one and one-half hours while per-' mitting the skeins to. shrink freely without untwisting or snarling. These skeins were then allowed to dry and cool and theliveliness of theyarn tested." The twist liveliness before setting was 11.25 units'and after treatment was found to be 0.5 unit, the yarn-set showed an angle of 75, and the yarn was entirely satis factory for further textile'operatlons. v

The twist liveliness-referred to above is measured by means of a test which gives a quantitaapart, care being taken not to back up the twist inthe handling of the yam. A weight of 0.5 gram is hung at the midpoint of the yarn free to twist up on itself. The distance betweenthe. two clamps, measured in centimeters, at the point where the yarn begins to twist up on itself,

is taken as the measure, in units, of twist liveliness. Therefore, the smaller this distance, the

lower is the unit value of twist liveliness and the better the twist-setting in the yarn.

This test was designed to measure the twist liveliness of yarns of the customary denier of sheer, full-fashioned hosiery, that is, from 20 to 50 denier. Obviously, it will be necessary to increase weight at the midpoint of the yarn when the test is applied to yarns of materially heavier denier.

The angular degree of yarn-set referred to throughout the specification and claims is measured in the following manner: The yarn to be tested is wound around a wedge-shaped blade having an angle of 23 so that the yarn is bent through an angle of 157. The wedge carrying th yarn is immersed in boiling water for thirty minutes. This is a drastic setting treatment and will set the yarn to the degree that it was not yarn-set by the twist-setting operation. The

' yarn is then removed fromthe wedge by cutting will not be satisfactory for use in weaving or knitting processes. For yarns comprising very heavy denier filaments, the angular degree of yarn-set as measured in the manner described should preferably be materially less than 120.

Example I! A polyhexamethylene adipamide yarn similar to Example I, except that it had been sized with a partially hydrolyzed polyvinyl acetate size containing boric acid and polyethylene oxide as disclosed in the copending application of Daniel E. Strain, Serial No.. 357,755, filed September 21, l940, was wound on a bobbin carrying a removable collapsible shell. After winding, the shell was removed and collapsed to permit the unrestrained shrinking of the yarn during twistsetting. This yarn was then twist-set under the same conditions and for the same length of time as in Example I, after which the liveliness wasfound to be 3.5 units, th yam-set showed an angle performance was" satisfactory. I

Example III Thirty-denier, iii-filament polyhexamethylene adipamide yarn-of 2 turns perinch twist was uptwisted with the addition of 29 turns-twist. Between the balloon pigtail of the uptwister and the take-up bobbin, the yarn under a tension of of the brass bar and subject to the influence of gravity. The movable clamp is then brought toward the fixed clamp and at a definite distance between the two ends of the yarn, the yarn begins 3 grams was passed through a moistening device and then through a slot 3% inches long in a copper block electrically heated to 115 C. This yarn after this treatment was found to have a twist liveliness of 3.1 units and a yarn-set of The yarn was subsequently coned and knit without diiliculty because of liveliness.

, result; consequently-"the twist-settingshould-hm Example I V A BO-denier, -filament, -turn sized polyhexamethylene adlpamide yarn in the form of a warp was moistened by meansof a roller running in a trough of water. I After this moistening, the warp was run through a'heating tunnel at 105 C. This tunnel was 21feet long and the j methylene adipamide yarn which had. been sized was twist-set on a rigid bobbin-to which it-had been wound 'under a tension of .18 grams. i iThiS yarn was twist-set for one andone-half hours under the conditions of 170 F. and 88% ;relative I humidity. This yamwas'ioundto have atwis't .3 liveliness of 5.5 units'and wasgfound to -kink ob-f jectionably during knitting; A similar, sample" -VI of sized yarn was wound toskeins and was-'twistset under the same conditionsaSFdescribBdjabOve 7 except that the skeins wereireefto shrink... The, yarn was then foundto have a twist liveliness of 2 units and the knitting. pel'forrnance'fwas satisfactory. This example'.-' is included-to show the difference between the twist, livelinesscf yarn which has been twist-set without permitting shrinkage and that where shrinkage is allowed -l Although this invention has been described terms of specific examples, it will be readily un-:'

derstood that numerousn odiflcationsmay be made while still remaining within the scope of this invention. In Examples 1, II, and V, the

' conditions of 'twis'tesetting were-170 B. and 88% relative humidityiy The optimum conditions for twist-setting in an atmosphere oi. elevated temperature and highf'relative humidity to obtain a low twist liveliness, according to this invention. lie between 170 and 190 F. with-a relativehu- ,midity between and However, twistse'tting may be carried out to give a yarn which does not have excessive liveliness even if the temperature of setting reduced as: low as --F. To achieve satisfactory results. the relative hu -ff midity of the atmosphere of twist-setting must be, maintained above 50%. and it is preferred to operate with a humidity above 75%. Instead of subjecting the yarn to atmospheric conditions of a high temperature and high humidity, it maybe subjected to water having a temperature. of between 135 F. and"190"-I A 'temperature in excess of F. is preferred; i of course, it will; be readily understood" that ii -thetwist-setting conditions are made too'idrastic,;'yarnsetting wil be carried-out at a temperature injexcessjof gl9ll F. The temperature used depend, to some extent, upon the time of treatment and theweight and particular character-"of the Nylon ya'rn'. 1It;""

is important that the exposure to these j'condi-.-*: tions be maintained long enough so that allot. the underlying layers of yarn be exposed to" the) hot, wet conditions. Thetimeand temperature"..- employed in the treatment may be readily deter; .mined by the above-described twist-settingf'and',

yarn-settingtests, a

It will be obvious, of course, that the heat may be provided in any oneof several ways. For ex ample, hot water, steam, heated air, heated metal plates, infra red, hot gases or vapors, warmalcohol or similar swelling agents may be used.

, sufli'cient twist to give trouble, in a textile operation, from twist liveliness.

Although this invention hasbeendescribed in 5 the examples in terms of twist-setting of ,30-

denier yarn which has been twisted to 30 turns per inch, the method of the present invention isapplicable to yarns of different deniers. and degrees of twist. Other things being equal, it is The degreeiof twistin aj-yarn of a given diameter is determined by the ,numberof turns per inchiQ-The degree of-twistin yarns of different.

diameters'is (determined more: accurately by the fhelixf'anglef bfjtwist as described in An Intro- .duction to the MicroeAnalysis of Yarn Twist" by E. R Schwarz, vpublishediin the Journal of the can be utilized in setting the twist in such a yarn by'fii'st twisting the same to a greater extent than required, twist-setting in accordance 1 with the present invention and then back-twisting to the desired twist For example, to pro-' duce a 30-denier, 50-turn yarn, the yarn can be twisted to 55 turns per inch,- twist-set and then back-twisted 5 turns per inch. The resulting vyam will not have an objectionable live:

liness.

I In order that shrinkage ma'ygbef a llow'ed-l I while the twist-setting processis going on, itis necessary that the tension-of the yarngjduringt twist-setting be kept below certain limit's.;;-It= has been found that the residualshrinka'ge of a twist-set yarn varies in direct proportion with the tensionto which it was subjected while being i; twist-set." .Sinc'e'thejtwist liveliness of the yarn is proportional toith'e residual shrinkage, it will be readily seen that thetWi'stIliveliness will be proportional tothe tension during twist-setting. i In order that twist liveliness be reduced to a sat-' I isfactory degree, thejtens'iori*during twist-setting shouldnot exceed 0.66 gram per'denierand it is preferred that the tension notlexceedloA gram per denier; As for the lower limit'of.ten-- sion, it is, only necessary that sufiicient tension beapplied; to the yarn to prevent, it from loop-- agreeaduring'setting'. This may easily be demlnedby one skilled in the art.-

is sho bev arried'out either whilethe yarn is station- Textilelnstitute for March,'e.1933. .The' present invention-is applicable to reduce twist livelinessin I Nylon yarns having on the basis of the yarn diameter, a minimum twist commensurate to a 20;turn' per inchtwist-in a 30-denier yarn. v I

@Heretofore, particular difiiculty has been encountered from the twist liveliness of yarns hav- 7 I ing a very high twist, for example, a crepe Nylon I yarn of 30 denier having a twist of 50 turns'per inch., The principles of the present invention- 1 in the examples, this process may aryi 'or moving. The twist-setting may be per iormedwhen the yarn is loosely held in skeins withjonly .suflicient tension'to'prevent looping]. or it may be loosely wound on a-bobbin." Also, af1" i collapsible'bobbin maybe used as shown in Ex-j'-. {ample II.- It is sometimes advantageous. to per- =form fithe twist-setting operation while the yarn. is travelingtrom. one package to another ,or. I ."whilein "a warp as in-Examples II, III: and In certain instances, twist-setting mayfbe car---'; 'ried out in conjunction with the sizing operation so that, after the yarn is-sized, it canthen be. I twist-set while still on-the-run before winding up. Of course',.the twist-settingst'ep can be car-..'

ried out in two or more stages prior to the textile operation. For example, in the orderly operation of a plant, there may not be sufficient time to carry out fully the twist-setting on a size I claim:

1. The process of twist-setting a Nylon yarn to reduce the twist-liveliness thereof which comprises subjecting said yarn to a hot, wet treatbobbin but there may be time available during 5 ment involving a temperature between 135 F.

the subsequent coning operation. In such a case, the twist-setting operation may be carried out in both places for suitable periods of time. As is shown in the examples, this process is, of

course, applicable to both sized and unsized lo age effected, thus giving a tighter weave.

The present invention is also applicable to the twist-setting of Nylon yarn in which a minor proportion (less than 50%) 'of the filaments is composed of other materialsthan Nylon, for example, cotton, regenerated cellulose, cellulose acetate, etc. The term Nylon yarn," therefore. includes all yarns in which at least 50% 'of the filaments or fibers are composed of Nylon.

By this invention, *there is now provided a method ofsetting the twist in a yarn so that it will run smoothly in subsequent textile operations such as knitting and weaving without the danger of snarls and loops due to the twist liveliness. -At' t hesame time, the twist-setting is accomplished without the danger of so setting the yarn itself that the fabric subsequently made from the ,yarn would be unsatisfactory, for reasons such as laciness or poor stitch formation,

and 190 F. and a relative humidity in excess of 50% while maintaining the yarn under sufficiently low tensioning conditions to permit the same to shrink.

2. The process of twist-setting a Nylon yarn to reduce the twlst-liveliness thereof which comprises subjecting said yam to an atmosphere having a temperature between 135 F. and 190 F. and a relative humidity in excess of 50% while maintaining the yarn under sufliciently low tensioning conditions to permit the same to shrink.

3., Theprocess of twist-setting a Nylon yarn to reduce the twist-liveliness thereof which comprises subjecting said yarn to a hot, wet treatment involving a temperature between 135 F.

and 190 F. and a relative humidity .infexcess of 50% while maintaining the. yarn under tensioning conditions not to exceed 0.66 gram per denier.

4. The process of twist-setting a Nylon yarn to reduce the twist-liveliness thereof which comprises subjecting said yarn to an atmosphere having a temperature between 135 F. and 190 F. and a relative humidity in excess of 50% while maintaining the yarn under tensioning conditions not to exceed 0.66 gram per denier.

and a relative humidity between 85% and 100% while maintaining the yarn under tensioning conditions not to exceed 0.66 gram per denier.

. 6. The process of twist-setting 9. Nylon yarn to reduce the twist-liveliness thereof which comeither of which is readily discernible by the prises subjecting saidyamtoan atmosphere hayknitter.

Another advantage of this invention is that thegtwist liveliness is reduced more than it is .when the yarn is set by means of steam without permitting shrinkage, even if the matter of yarnset is completely ignored. For example, it 'is verydiflicult to set properly a twist of turns per inch in 30-denier yarn according to the prior art procedure. It can be easily andsuccessfully ing a temperature between 170 F. and 190 F. and a relative humidity in excess of 50% while maintaining the yarn undertensioning conditions not to exceed 0.66 gram per denier.

7. The process of twist-setting aNylon yarn to reduce the twist-liveliness thereof which comprises subjecting said yarn to an atmosphere having a temperature between 170 F. and 190 F. and arelative humidity between and set according to this invention. Since, by this :50 while maintaining t yarn under tensioning invention, the yarn does not become set, it'is 'a very important aspect.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the nature andloa spirit of the invention, it is to be understood that the invention is not to be limited to the details described herein except as set forth in the appended claims.

' yarn produced in accordance with. the process of claim 3.

JOHN BLANCHARD MILES, JR. 

